Changes in Spinal and Corticospinal Excitability in Patients with Chronic Ankle Instability: A Systematic Review with Meta-Analysis

Soleus arthrogenic muscle inhibition following acute lateral ankle sprain correlates with symptoms and ankle disability but not with postural control

BACKGROUND

Acute lateral ankle sprains (ALAS) are associated with long-term impairments and instability tied to altered neural excitability. Arthrogenic muscle inhibition (AMI) has been observed in this population; however, relationships with injury-related impairments are unclear, potentially due to the resting, prone position in which AMI is typically measured. Assessing AMI during bipedal stance may provide a better understanding of this relationship.

METHODS

AMI was assessed in 38 young adults (19 ALAS within 72 h of injury: 10 males, 21.4 ± 2.7 years; 19 healthy controls: 10 males, 21.9 ± 2.2 years; mean ± SD) using the Hoffmann reflex (H-reflex) during bipedal stance. Electrical stimulation was administered to identify the maximal H-reflex (Hmax) and maximal motor response (Mmax) from the soleus, fibularis longus, and tibialis anterior muscles. The primary outcome measure was the Hmax/Mmax ratio. Secondary outcomes included acute symptoms (pain and swelling), postural control during bipedal stance, and self-reported function.

RESULTS

No significant group-by-limb interactions were observed for any muscle. However, a significant group main effect was observed in the soleus muscle (F(1,35) = 6.82, p = 0.013), indicating significantly lower Hmax/Mmax ratios following ALAS (0.38 ± 0.20) compared to healthy controls (0.53 ± 0.16). Furthermore, lower Hmax/Mmax ratios in the soleus significantly correlated with acute symptoms and self-reported function but not with postural control.

CONCLUSION

This study supports previous evidence of AMI in patients with ALAS, providing insight into neurophysiologic impacts of musculoskeletal injury. Our results suggest that assessing AMI in a standing position following acute injury may provide valuable insight into how AMI develops and guide potential therapeutic options to curb and offset the formation of joint instability.

Physical Therapy Intervention Effects on Alteration of Spinal Excitability in Patients With Chronic Ankle Instability: A Systematic Review and Meta-analysis

CONTEXT

Chronic ankle instability (CAI) is a common injury in athletes. Different forms of physical therapy have been applied to the population with CAI to assess their impact on spinal excitability.

OBJECTIVE

The purpose of this systematic review and meta-analysis was to investigate the effectiveness of various physical therapy interventions on the alteration of spinal excitability in patients with CAI.

DATA SOURCES

Four databases (EMBASE, MEDLINE, Cochrane CENTRAL, and Scopus) were searched from inception to November 2022.

STUDY SELECTION

A total of 253 studies were obtained and screened; 11 studies on the effects of physical therapy intervention on the alteration of spinal excitability in patients with CAI were identified for meta-analysis.

STUDY DESIGN

Systematic review and meta-analysis.

LEVEL OF EVIDENCE

Level 3a.

DATA EXTRACTION

A total of 11 studies that included the maximal Hoffmann reflex normalized by the maximal muscle response (H/M ratio) in the peroneus longus and soleus muscles were extracted and summarized. The quality of the studies was assessed using the PEDro scale.

RESULTS

The extracted studies had an average PEDro score of 4.7 ± 1.4, indicating that most of them had fair-to-good quality. The physical therapy interventions included cryotherapy, taping, mobilization, proprioceptive training, and dry needling. The overall effects showed that the H/M ratios of the peroneus longus (P = 0.44, I2 = 0%) and soleus (P = 0.56,I2 = 22%) muscles were not changed by physical therapy in patients with CAI.

CONCLUSION

The meta-analysis indicated that physical therapy interventions such as cryotherapy, taping, mobilization, proprioceptive training, and dry needling do not alter the spinal excitability in patients with CAI. Given that only 1 study reported ineffective changes in spinal excitability with dry needling, more research is essential to establish and validate its efficacy.

PROSPERO REGISTRATION

CRD42022372998.

Patients with chronic ankle instability exhibit increased sensorimotor cortex activation and correlation with poorer lateral balance control ability during single-leg stance: a FNIRS study

Introduction

Chronic Ankle Instability (CAI) is a musculoskeletal condition that evolves from acute ankle sprains, and its underlying mechanisms have yet to reach a consensus. Mounting evidence suggests that neuroplastic changes in the brain following ankle injuries play a pivotal role in the development of CAI. Balance deficits are a significant risk factor associated with CAI, yet there is a scarcity of evidence regarding the sensorimotor cortical plasticity related to balance control in affected individuals. This study aims to evaluate the differences in cortical activity and balance abilities between patients with CAI and uninjured individuals during a single-leg stance, as well as the correlation between these factors, in order to elucidate the neurophysiological alterations in balance control among patients with CAI.

Methods

The study enrolled 24 patients with CAI and 24 uninjured participants. During single-leg stance, cortical activity was measured using a functional near-infrared spectroscopy (fNIRS) system, which included assessments of the pre-motor cortex (PMC), supplementary motor area (SMA), primary motor cortex (M1), and primary somatosensory cortex (S1). Concurrently, balance parameters were tested utilizing a three-dimensional force platform.

Results

Independent sample t-tests revealed that, compared with the uninjured individuals, the patients with CAI exhibited a significant increase in the changes of oxyhemoglobin concentration (ΔHbO) during single-leg stance within the left S1 at Channel 5 (t = 2.101, p = 0.041, Cohen's d = 0.607), left M1 at Channel 6 (t = 2.363, p = 0.022, Cohen's d = 0.682), right M1 at Channel 15 (t = 2.273, p = 0.029, Cohen's d = 0.656), and right PMC/SMA at Channel 11 (t = 2.467, p = 0.018, Cohen's d = 0.712). Additionally, the center of pressure root mean square (COP-RMS) in the mediolateral (ML) direction was significantly greater (t = 2.630, p = 0.012, Cohen's d = 0.759) in the patients with CAI. Furthermore, a moderate positive correlation was found between ML direction COP-RMS and ΔHbO2 in the M1 (r = 0.436; p = 0.033) and PMC/SMA (r = 0.488, p = 0.016), as well as between anteroposterior (AP) direction COP-RMS and ΔHbO in the M1 (r = 0.483, p = 0.017).

Conclusion

Patients with CAI demonstrate increased cortical activation in the bilateral M1, ipsilateral PMC/SMA, and contralateral S1. This suggests that patients with CAI may require additional brain resources to maintain balance during single-leg stance, representing a compensatory mechanism to uphold task performance amidst diminished lateral balance ability in the ankle joint.

Deficits in neurocognitive performance in patients with chronic ankle instability during a neurocognitive balance task - A retrospective case-control study

OBJECTIVES

To assess the neurocognitive performance while maintaining balance of patients experiencing CAI compared to healthy controls. In patients with CAI, the affected limb was also compared to the contralateral limb.

DESIGN

A retrospective case-control study.

SETTING

Laboratory study.

PARTICIPANTS

We included 27 patients with CAI and 21 healthy controls.

METHODS

The study consisted of two sessions, namely familiarisation and experimentation, which were scheduled with a gap of at least one week between them. During the experimental trial, both groups performed the Y-Balance Test and Reactive Balance Test once on each limb.

MAIN OUTCOME MEASURES

The main outcome measures are accuracy and visuomotor response time (VMRT) calculated via video-analysis and with the Fitlight™-hardware and software respectively during the Reactive Balance Test (RBT).

RESULTS

No data was excluded from the final analysis. Patients with CAI exhibited significantly lower accuracy than healthy controls, with a mean difference of 8.7% (±3.0)%. There were no differences for VMRT between groups. Additionally, no significant differences were observed between the affected and contralateral limb of the patient group for both accuracy and VMRT.

CONCLUSIONS

Patients with CAI showed lower accuracy, but similar VMRT compared to healthy controls during a neurocognitive balance task, indicating impaired neurocognitive function. Patients exhibit comparable speed to healthy individuals when completing neurocognitive balance tasks, yet they display a higher frequency of accuracy errors in accurately perceiving their environment and making decisions under time constraints. Future research should gain more insights in which other cognitive domains are affected in patients with CAI for a better grasp of this condition's underlying mechanism.

Test-retest, intra- and inter-rater reliability of the reactive balance test in patients with chronic ankle instability

Introduction

The Reactive Balance Test (RBT) could be a valuable addition to research on chronic ankle instability (CAI) and clinical practice, but before it can be used in clinical practice it needs to be reliable. It has already been proven reliable in healthy recreational athletes, but not yet in patients with CAI who have shown persistent deficits in dynamic balance. The study aimed to determine the test-retest, intra-, and inter-rater reliability of the RBT in patients with CAI, and the test-retest and inter-rater reliability of the newly developed RBT score sheet.

Methods

We used a repeated-measures, single-group design to administer the RBT to CAI patients on three occasions, scored by multiple raters. We included 27 participants with CAI. The study used multiple reliability measures, including Pearson r, intra-class correlations (ICC), standard error of measurement (SEM), standard error of prediction (SEP), minimal detectable change (MDC), and Bland-Altman plots, to evaluate the reliability of the RBT's outcome measures (visuomotor response time and accuracy). It also assessed the test-retest and inter-rater reliability of the RBT score sheet using the same measures.

Results

The ICC measures for test-retest reliability were similar for accuracy (0.609) and VMRT (0.594). Intra-rater reliability had high correlations and ICCs for accuracy (r = 0.816, ICC = 0.815) and VMRT (r = 0.802, ICC = 0.800). Inter-rater reliability had a higher ICC for VMRT (0.868) than for accuracy (0.690).

Conclusion

Test-retest reliability was moderate, intra-rater reliability was good, and inter-rater reliability showed moderate reliability for accuracy and good reliability for VMRT. Additionally, the RBT shows robust SEM and mean difference measures. The score sheet method also demonstrated moderate test-retest reliability, while inter-rater reliability was good to excellent. This suggests that the RBT can be a valuable tool in assessing and monitoring balance in patients with CAI.

Exercise combined with electrical stimulation for the treatment of chronic ankle instability - A randomized controlled trial

PURPOSE

To compare the short, medium, and long-term effects of balance exercises combined with either peroneal neuromuscular electrical stimulation (NMES) or peroneal transcutaneous electrical nerve stimulation (TENS) on dynamic postural control and patient reported outcome measures (PROMs) in patients with chronic ankle instability (CAI).

METHODS

Thirty-four participants with CAI were randomly assigned to a 12-session home based exercise program combined with NMES (Ex-NMES) or TENS (Ex- TENS). Baseline postural control was tested with the modified Star Excursion Balance Test (mSEBT) and time to stabilization (TTS) after a single-leg drop-jump. The self-reported function was measured using the Cumberland Ankle Instability Tool (CAIT), the Identification of Functional Ankle Instability (IdFAI), and the Sports subscale of the Foot and Ankle Ability Measure (FAAMSport).

RESULTS

Both groups showed significant improvements in all self-reported outcome measures at the 12-month follow-up. Subjects in the Ex-NMES group had significantly better IdFAI (-4.2 [95% CI -8.1, -0.2]) and FAAMSport (13.7 [95% CI 2.2, 25.2]) scores at 6- and 12-month follow-up, respectively, compared to the Ex-TENS group. Medium to large between-group effect sizes were observed in self-reported functional outcomes and the mSEBT.

CONCLUSION

The consistent trend of improvement in self-reported functional outcomes when training is combined with NMES compared with training with TENS may indicate a potential benefit that should be further investigated as a treatment for patients with CAI.

What interventions can treat arthrogenic muscle inhibition in patients with chronic ankle instability? A systematic review with meta-analysis

PURPOSE

To identify, critically appraise, and synthesize the existing evidence regarding the effects of therapeutic interventions on arthrogenic muscle inhibition (AMI) in patients with chronic ankle instability (CAI).

MATERIALS AND METHODS

Two reviewers independently performed exhaustive database searches in Web of Science, PubMed, Medline, CINAHL, and SPORTDiscus.

RESULTS

Nine studies were finally included. Five types of disinhibitory interventions were identified: focal ankle joint cooling (FAJC), manual therapy, fibular reposition taping (FRT), whole-body vibration (WBV), and transcranial direct current stimulation (tDCS). There were moderate effects of FAJC on spinal excitability in ankle muscles (g = 0.55, 95% CI = 0.03-1.08, p = 0.040 for the soleus and g = 0.54, 95% CI = 0.01-1.07, p = 0.046 for the fibularis longus). In contrast, manual therapy, FRT, WBV were not effective. Finally, 4 weeks of tDCS combined with eccentric exercise showed large effects on corticospinal excitability in 2 weeks after the intervention (g = 0.99, 95% CI = 0.14-1.85 for the fibularis longus and g = 1.02, 95% CI = 0.16-1.87 for the tibialis anterior).

CONCLUSIONS

FAJC and tDCS may be effective in counteracting AMI. However, the current evidence of mainly short-term studies to support the use of disinhibitory interventions is too limited to draw definitive conclusions.

Effects of Kinesio taping on lower limb biomechanical characteristics during unexpected jumping in patients with chronic ankle instability

PURPOSE

The current biomechanical research on the application of Kinesio taping (KT) to patients with chronic ankle instability (CAI) has focused on testing the expected movements. However, unexpected movements are more common in actual sports. Therefore, the present study aimed to investigate the effects of KT on the biomechanical characteristics of the knee and ankle joints during unexpected jumping movements.

METHODS

Twenty-one patients with unilateral CAI were recruited to capture the biomechanical parameters during unexpected jumping movements under different interventions: no taping (NT), placebo taping (PT), and KT. A one-way repeated measures analysis of variance was used to compare the differences in knee and ankle biomechanical characteristics among patients with CAI between the three intervention conditions.

RESULTS

At initial contact, the KT group demonstrated a significant decrease in ankle plantarflexion and knee flexion angles compared to the NT group (p < 0.05). At the early landing phase, the KT group had a significant increase in peak ankle dorsiflexion angle, peak ankle eversion angle, peak ankle dorsiflexion moment, and peak ankle eversion moment compared to the NT and PT groups (p < 0.05). Furthermore, the KT group had a significantly reduced peak knee flexion angle, peak knee eversion angle, and peak vertical ground reaction force (p < 0.05) compared to the NT and PT groups.

CONCLUSION

KT significantly improves the sprain-prone touchdown posture of patients with CAI. And reducing the risk of ankle sprains during the early landing phase by promoting ankle dorsiflexion and eversion angles and moments.

Efficacy of resistance training with elastic bands compared to proprioceptive training on balance and self-report measures in patients with chronic ankle instability: A systematic review and meta-analysis

BACKGROUND

Proprioceptive training and resistance training are physiotherapy treatment methods for Chronic Ankle Instability (CAI).

OBJECTIVE

To compare the efficacy of proprioceptive training to resistance training with elastic bands for treating CAI as measured by the Star Excursion Balance Test (SEBT), the Foot and Ankle Ability Measure (FAAM), and the Cumberland Ankle Instability Tool (CAIT).

METHOD

Our systematic study and meta-analysis was based on the PICOS and PRISMA protocols. The PubMed, PEDro, and ScienceDirect databases were searched for randomized clinical trials on proprioceptive and resistance training. Risk of bias was assessed according to Cochrane guidelines and quality of evidence was reported using the Grading of Recommendations Assessment, Development, and Evaluation approach (GRADE).

RESULTS

Five studies involving 259 patients were included in the review. According to the findings of the meta-analysis, proprioceptive training was similarly effective with resistance training in SEBT and FAAM measures. Compared with resistance exercise, proprioceptive training demonstrated some benefits in CAIT scores (weighted mean difference [WMD] = -2.21, 95% CI = -4.05-0.36), but these intervention results were not clinically significant (MDC, MCID score >3 points).

CONCLUSION

Low-quality evidence from studies showed that neither of the interventions was superior on the SEBT or the FAAM scores in individuals with CAI because no clinically significant differences were found. More high-quality studies comparing the two interventions are needed to draw firm conclusions.

Role of interventions targeting plantar cutaneous receptors in improving postural control in chronic ankle instability: A systematic review with meta-analysis

INTRODUCTION

Chronic ankle instability (CAI) is a disorder that occurs after one or more acute ankle sprains and is characterised by persistent symptoms which include episodes of ''giving way'' a sensation of instability, recurrent ankle sprains, and functional deficits. Despite of effective treatment strategies a comprehensive approach is needed that can break this continuum of disability and improve the postural control. A systematic review with meta-analysis assessing the effectiveness of interventions targeting plantar cutaneous receptors for improving postural control in individuals with chronic ankle instability.

METHODS

The systematic review with meta-analysis was performed following PRISMA guidelines. Outcome measure used to evaluate the improvement in which static postural control was assessed on SLBT (Single limb balance test) and COP (Centre of pressure) whereas dynamic postural control was assessed on SEBT (star excursion balance test) and scores expressed as mean ± SD and random-effects model were performed, and heterogeneity between the studies was calculated using the I2 statistic.

RESULTS

A total of 168 CAI populations were included among the 8 selected studies in the meta-analysis. In which,5 studies using Plantar massage and 3 studies using foot insole were assessed, with moderate to high quality on the Pedro scale (range 4-7). For single and six-sessions of plantar massage showed insignificant effect on SLBT COP and for the single session of custom moulded FO showed insignificant effect on SEBT.

CONCLUSION

The meta-analysis showed non-significant pooled results for plantar massage and foot orthotics on static and dynamic postural control when assessed on postural outcome measures. Further high-quality evidence-based trials would be required to highlight the importance of sensory targeted approaches to treat the postural instability in CAI patients.

Brain Neuroplasticity Related to Lateral Ankle Ligamentous Injuries: A Systematic Review

BACKGROUND

Lateral ankle sprains are the most common ankle injuries in sports and have the highest recurrence rates. Almost half of the patients experiencing lateral ankle sprains develop chronic ankle instability. Patients with chronic ankle instability experience persistent ankle dysfunctions and detrimental long-term sequelae. Changes at the brain level are put forward to explain these undesirable consequences and high recurrence rates partially. However, an overview of possible brain adaptations related to lateral ankle sprains and chronic ankle instability is currently lacking.

OBJECTIVE

The primary purpose of this systematic review is to provide a comprehensive overview of the literature on structural and functional brain adaptations related to lateral ankle sprains and in patients with chronic ankle instability.

METHODS

PubMed, Web of Science, Scopus, Embase, EBSCO-SPORTDiscus and Cochrane Central Register of Controlled Trials were systematically searched until 14 December, 2022. Meta-analyses, systematic reviews and narrative reviews were excluded. Included studies investigated functional or structural brain adaptations in patients who experienced a lateral ankle sprain or with chronic ankle instability and who were at least 18 years of age. Lateral ankle sprains and chronic ankle instability were defined following the recommendation of the International Ankle Consortium. Three authors independently extracted the data. They extracted the authors' name, publication year, study design, inclusion criteria, participant characteristics, the sample size of the intervention and control groups, methods of neuroplasticity testing, as well as all means and standard deviations of primary and secondary neuroplasticity outcomes from each study. Data reported on copers were considered as part of the control group. The quality assessment tool for observational and cross-sectional studies was used for the risk of bias assessment. This study is registered on PROSPERO, number CRD42021281956.

RESULTS

Twenty articles were included, of which only one investigated individuals who experienced a lateral ankle sprain. In all studies combined, 356 patients with chronic ankle instability, 10 who experienced a lateral ankle sprain and 46 copers were included. White matter microstructure changes in the cerebellum have been related to lateral ankle sprains. Fifteen studies reported functional brain adaptations in patients with chronic ankle instability, and five articles found structural brain outcomes. Alterations in the sensorimotor network (precentral gyrus and supplementary motor area, postcentral gyrus and middle frontal gyrus) and dorsal anterior cingulate cortex were mainly found in patients with chronic ankle instability.

DISCUSSION

The included studies demonstrated structural and functional brain adaptations related to lateral ankle sprains and chronic ankle instability compared to healthy individuals or copers. These adaptations correlate with clinical outcomes (e.g. patients' self-reported function and different clinical assessments) and might contribute to the persisting dysfunctions, increased re-injury risk and long-term sequelae seen in these patients. Thus, rehabilitation programmes should integrate sensorimotor and motor control strategies to cope with neuroplasticity related to ligamentous ankle injuries.

Effects of plantar-sensory treatments on postural control in chronic ankle instability: A systematic review and meta-analysis

OBJECTIVE

This study aimed to examine the effects of plantar-sensory treatments on postural control in individuals with chronic ankle instability (CAI).

METHODS

This study was registered in PROSPERO (registration number CRD42022329985) on May 14, 2022. An extensive search was performed in Pubmed, Embase, Cochrane, Web of Science, and Scopus to identify the potential studies on plantar-sensory treatments affecting postural control before May 2022. The methodological quality of involved studies was assessed using the scale of Physiotherapy Evidence Database (PEDro). The Cochrane Tool and the Risk of Bias in Non-randomized Studies of Interventions assessment tool were used to evaluate the risk of bias in randomised controlled trials (RCTs) and non-RCTs respectively. RevMan 5.4 was utilised to calculate the standardised mean difference (SMD), with 95% confidence interval (CI).

RESULTS

Eight RCTs with a mean PEDro rating of 6 and four non-RCTs with a mean PEDro rating of 4.75 were included in the quantitative analysis. The types of plantar-sensory treatments included plantar massage, whole-body vibration and textured surface-stimulation treatment. A significant effect of static balance with eyes open (SMD = -0.54; 95% CI: -0.81 to -0.27; p < 0.001) was found and subgroup analysis showed that plantar massage (SMD = -0.49; 95% CI: -0.84 to -0.14; p = 0.006) and whole-body vibration (SMD = -0.66; 95% CI: -1.12 to -0.19; p = 0.005) had positive effects. In the subgroup analysis of anterior dynamic balance, whole-body vibration revealed a significant increase (SMD = 0.60; 95% CI: 0.06-1.14; p = 0.03). The pooled results or subgroup analysis including eyes-closed static balance and other directions of dynamic balance indicated no significant difference (p > 0.05).

CONCLUSIONS

This meta-analysis indicated that plantar-sensory treatments could improve postural control in CAI, especially the treatments of plantar massage and long-term whole-body vibration.

Case report: High-frequency repetitive transcranial magnetic stimulation for treatment of hereditary spastic paraplegia type 11

Hereditary spastic paraplegia (HSP) is a heterogeneous group of inherited neurodegenerative disorders that currently have no cure. HSP type 11 (SPG11-HSP) is a complex form carrying mutations in the SPG11 gene. Neuropathological studies demonstrate that motor deficits in these patients are mainly attributed to axonal degeneration of the corticospinal tract (CST). Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive technique that can induce central nervous system plasticity and promote neurological recovery by modulating the excitability of cortical neuronal cells. Although rTMS is expected to be a therapeutic tool for neurodegenerative diseases, no previous studies have applied rTMS to treat motor symptoms in SPG11-HSP. Here, we report a case of SPG11-HSP with lower extremity spasticity and gait instability, which were improved by applying high-frequency rTMS (HF-rTMS) at the primary motor cortex (M1). Clinical and physiological features were measured throughout the treatment, including the Modified Ashworth Scale (MAS), Berg Balance Scale (BBS), the timed up and go (TUG) test and the 10-meter walk test time (10 MWT). The structure and excitability of the CST were assessed by diffusion tensor imaging (DTI) and transcranial magnetic stimulation (TMS), respectively. After treatment, the patient gained 17 points of BBS, along with a gradual decrease in MAS scores of the bilateral lower extremity. In addition, the TUG test and 10 MWT improved to varying degrees. TMS assessment showed increased motor evoked potential (MEP) amplitude, decreased resting motor threshold (RMT), decreased central motor conduction time (CMCT), and decreased difference in the cortical silent period (CSP) between bilateral hemispheres. Using the DTI technique, we observed increased fractional anisotropy (FA) values and decreased mean diffusivity (MD) and radial diffusivity (RD) values in the CST. It suggests that applying HF-rTMS over the bilateral leg area of M1 (M1-LEG) is beneficial for SPG11-HSP. In this study, we demonstrate the potential of rTMS to promote neurological recovery from both functional and structural perspectives. It may provide a clinical rationale for using rTMS in the rehabilitation of HSP patients.

Revisiting the use of Hoffmann reflex in motor control research on humans

Research in movement science aims at unravelling mechanisms and designing methods for restoring and maximizing human functional capacity, and many techniques provide access to neural adjustments (acute changes) or long-term adaptations (chronic changes) underlying changes in movement capabilities. First described by Paul Hoffmann over a century ago, when an electrical stimulus is applied to a peripheral nerve, this causes action potentials in afferent axons, primarily the Ia afferents of the muscle spindles, which recruit homonymous motor neurons, thereby causing an electromyographic response known as the Hoffmann (H) reflex. This technique is a valuable tool in the study of the neuromuscular function in humans and has provided relevant information in the neural control of movement. The large use of the H reflex in motor control research on humans relies in part to its relative simplicity. However, such simplicity masks subtleties that require rigorous experimental protocols and careful data interpretation. After highlighting basic properties and methodological aspects that should be considered for the correct use of the H-reflex technique, this brief narrative review discusses the purpose of the H reflex and emphasizes its use as a tool to assess the effectiveness of Ia afferents in discharging motor neurones. The review also aims to reconsider the link between H-reflex modulation and Ia presynaptic inhibition, the use of the H-reflex technique in motor control studies, and the effects of ageing. These aspects are summarized as recommendations for the use of the H reflex in motor control research on humans.

Virtual reality does not fool the brain only: spinal excitability changes during virtually simulated falling

Virtual reality (VR) is known to induce substantial activation of brain's motor regions. It remains unclear to what extent virtual reality can trigger the sensorimotor system, and more particularly, whether it can affect lower nervous levels. In this study, we aimed to assess whether VR simulation of challenging and stressful postural situations (Richie's plank experience) could interfere with spinal excitability of postural muscles in 15 healthy young participants. The H-reflex of the triceps surae muscles was elicited with electrical nerve stimulation while participants were standing and wearing a VR headset. Participants went through several conditions, during which stimulations were evoked: standing still (noVR), standing in VR on the ground (groundVR), standing on the edge of a building (plankVR), and falling from the building (fallingVR). Myoelectrical activity of the triceps surae muscles was measured throughout the experiment. Leg and head movements were also measured by means of accelerometers to account for body oscillations. First, no differences in head rotations and myoelectrical activity were to be noted between conditions. Second, triceps H-reflex (H_MAX/M_MAX) was not affected from noVR to groundVR and plankVR. The most significant finding was a drastic decrease in H-reflex during falling (-47 ± 26.9% between noVR and fallingVR, P = 0.015). It is suggested that experiencing a postural threat in VR efficiently modulates spinal excitability, despite remaining in a quiet standing posture. This study suggests that simulated falling mimics the neural adjustments observed during actual postural challenge tasks.NEW & NOTEWORTHY The present study showed a modulation of spinal excitability induced by virtual reality (VR). In the standing position, soleus H-reflex was downmodulated during a simulated falling, in the absence of apparent changes in body oscillations. Since the same behavior is usually observed during real falling, it was suggested that the visual cues provided by VR were sufficiently strong to lead the neuromuscular system to mimic the actual modulation.

Conduction Velocity of Spinal Reflex in Patients with Acute Lateral Ankle Sprain

Recent literature has highlighted altered spinal-reflex excitability following acute lateral ankle sprain (ALAS), yet there is little information on the conduction velocity of spinal reflex pathways (CV-SRP) in these patients. Therefore, we aimed to investigate the effects of ALAS on the CV-SRP. We employed a cross-sectional study with two groups: ALAS (n = 30) and healthy controls (n = 30). The CV-SRP of the soleus, fibularis longus, and tibialis anterior was assessed using the H-index method. As secondary outcomes, H-reflex and M-wave latencies were assessed as well as acute symptoms including ankle swelling, pain, and self-reported ankle function. Separate group-by-limb ANOVA with repeated measures revealed a significant interaction for soleus CV-SRP (p < 0.001) and H-reflex latency (p < 0.001), showing significant slower CV-SRP and longer H-reflex latency in the involved limb of the ALAS group compared with both limbs in the control group. However, there was no significant interaction or main effect in any other ankle muscles (p > 0.05). A further correlation analysis showed a significant relationship between CV-SRP and acute symptoms, including ankle swelling (r = −0.37, p = 0.048) and self-reported ankle function (r = 0.44, p = 0.017) in ALAS patients. These results suggest a disrupted functionality of the afferent pathway and/or synaptic transmission following ALAS. Level of Evidence: 4.

Spinal Reflex Excitability of Lower Leg Muscles Following Acute Lateral Ankle Sprain: Bilateral Inhibition of Soleus Spinal Reflex Excitability

Neural changes in the ankle stabilizing muscles following ankle sprains are thought to be one contributing factor to persistent ankle dysfunction. However, empirical evidence is limited. Therefore, we aimed to examine spinal reflex excitability of lower leg muscles following acute ankle sprains (AAS). We performed a case-control study with 2 groups consisting of 30 young adults with AAS and 30 aged-matched uninjured controls. Hoffmann reflex (H-reflex) testing was performed to estimate spinal reflex excitability of lower leg muscles: soleus, fibularis longus (FL), tibialis anterior (TA). Maximal H-reflex (H_max) and motor responses (M_max) were determined by delivering a series of electrical stimuli at the sciatic nerve. H_max/M_max ratios were calculated to represent normalized spinal reflex excitability. Separate group-by-limb analyses of variance (ANOVA) with repeated measures found there were no significant interactions for any of the muscles (SL: F_1,56 = 0.95, p = 0.33, FL: F_1,51 = 0.65, p = 0.42, TA: F_1,51 = 1.87, p = 0.18), but there was a significant main effect of group in the soleus (F_1,56 = 6.56, p = 0.013), indicating the H_max/M_max ratio of soleus in the AAS group was significantly lower bilaterally (AAS = 0.56 ± 0.19, control = 0.68 ± 0.17, p = 0.013), with no significant group differences in the other muscles (FL: F_1,51 = 0.26, p = 0.61, TA: F_1,51 = 0.93, p = 0.34). The bilateral inhibition of the soleus spinal reflex excitability following AAS may be significant in that it may explain bilateral sensorimotor deficits (postural control deficits) following unilateral injury, and provide insights into additional therapies aimed at the neural change.

Effects of Instrument Assisted Soft-Tissue Mobilization on Dynamic Balance in Those with Chronic Ankle Instability

Our objective was to examine the effectiveness of IASTM application to the FL on dynamic balance in individuals with CAI. Fifteen individuals (seven females, eight males, age = 26.07 ± 9.18 years, mass = 87.33 ± 24.07 kg, height = 178.83 ± 12.83 cm) with CAI, as determined by the Ankle Instability Instrument (AII) volunteered to participate. Participants completed two counterbalanced sessions (experimental and control), and we recorded measurements at two time points (pre- and post-). The application of IASTM to the FL muscle was carried out using Técnica Gavilán® instruments for 90 s during the intervention, and participants sat for 2 min during the control session. Dynamic balance was assessed using the Y-balance test (YBT). The interaction between session and time for anterior reach was significant (F1,14 = 5.26, p = 0.04, η2 = 0.27). Post-hoc tests revealed farther reach distances at post-test (71.02 ± 9.45 cm) compared to pre-test (66.57 ± 10.87 cm) when IASTM was applied (p = 0.02, Mean Difference = 4.45 cm, CI95 = 0.71–8.19 cm, Cohen’s d = 0.44). The interaction between session and time was not significant for posteromedial (F1,14 = 0.25, p = 0.62, η2 = 0.02, 1 − β = 0.08) or posterolateral reaches (F1,14 = 1.17, p = 0.30, η2 = 0.08, 1 − β = 0.17). The application of IASTM to the FL improved anterior reach of the YBT, but not posterolateral or posteromedial reaches in individuals with CAI. However, the 4.45 cm increase in anterior reach could have clinical implications for improved function.

The Immediate Carryover Effects of Peroneal Functional Electrical Stimulation Differ between People with and without Chronic Ankle Instability

Chronic ankle instability (CAI) is a common condition that may develop after an ankle sprain. Compared with healthy individuals, those with CAI demonstrate excessive ankle inversion and increased peroneal electromyography (EMG) activity throughout the stance phase of gait, which may put them at greater risk for re-injury. Functional electrical stimulation (FES) of targeted muscles may provide benefits as a treatment modality to stimulate immediate adaptation of the neuromuscular system. The present study investigated the effect of a single, 10 min peroneal FES session on ankle kinematics and peroneal EMG activity in individuals with (n = 24) or without (n = 24) CAI. There were no significant differences in ankle kinematics between the groups before the intervention. However, after the intervention, healthy controls demonstrated significantly less ankle inversion between 0-9% (p = 0.009) and 82-87% (p = 0.011) of the stance phase. Furthermore, a significant within-group difference was observed only in the control group, demonstrating increased ankle eversion between 0-7% (p = 0.011) and 67-81% (p = 0.006) of the stance phase after the intervention. Peroneal EMG activity did not differ between groups or measurements. These findings, which demonstrate that peroneal FES can induce ankle kinematics adaptations during gait, can help to develop future interventions for people with CAI.

Corticospinal activity during a single-leg stance in people with chronic ankle instability

PURPOSE

The aim of the study was to determine whether corticospinal excitability and inhibition of the tibialis anterior during single-leg standing differs among individuals with chronic ankle instability (CAI), lateral ankle sprain copers, and healthy controls.

METHODS

Twenty-three participants with CAI, 23 lateral ankle sprain copers, and 24 healthy control participants volunteered. Active motor threshold (AMT), normalized motor-evoked potential (MEP), and cortical silent period (CSP) were evaluated by transcranial magnetic stimulation while participants performed a single-leg standing task.

RESULTS

Participants with CAI had significantly longer CSP at 100% of AMT and lower normalized MEP at 120% of AMT compared to lateral ankle sprain copers (CSP_100%: p = 0.003; MEP_120%: p = 0.044) and controls (CSP_100%: p = 0.041; MEP_120%: p = 0.006).

CONCLUSION

This investigation demonstrate altered corticospinal excitability and inhibition of the tibialis anterior during single-leg standing in participants with CAI. Further research is needed to examine the effects of corticospinal maladaptations to motor control of the tibial anterior on postural control performance in those with CAI.

Understanding Athletic Trainers' Knowledge, Intervention, and Barriers Toward Arthrogenic Muscle Inhibition

CONTEXT

Arthrogenic muscle inhibition (AMI) is a common neurophysiological response to joint injury. While athletic trainers (ATs) are constantly treating patients with AMI, it is unclear how clinicians are using the available evidence to treat the condition.

OBJECTIVE

To investigate ATs' general knowledge, clinical practice, and barriers for treating AMI.

METHODS

A cross-sectional web-based survey was utilized. The survey was distributed to a random sample of 3000 ATs from the National Athletic Trainers' Association and through social media. 143 board certified ATs (age: 34.6 [10.3] y; experience: 11.7 [9.8] y) from various clinical settings and educational backgrounds were included in the analysis.

RESULTS

One hundred one respondents were able to correctly identify the definition of AMI. The majority of these respondents correctly reported that joint effusion (n = 95, 94.1%) and abnormal activity from joint receptors (n = 91, 90.1%) resulted in AMI. Of the 101 respondents, only 58 (57.4%) reported using disinhibitory interventions to treat AMI. The most frequently used evidence supported interventions were transcutaneous electrical nerve stimulation (n = 38, 65.5%), neuromuscular electrical stimulation (n = 33, 56.9%), and focal joint cooling (n = 25, 43.1%). The interventions used correctly most often based on current evidence were neuromuscular electrical stimulation (n = 29/33, 87.9%) and transcutaneous electrical nerve stimulation (n = 26/38, 68.4%). Overall, difficulty quantifying AMI (n = 62, 61.24%) and lack of education (n = 71, 76.2%) were most frequently perceived as barriers. Respondents that did not use disinhibitory interventions perceived lack of experience treating AMI, understanding the terminology, and access to therapeutic modalities more often than the respondents that reported using disinhibitory interventions.

CONCLUSION

Further education about concepts and treatment about AMI is warranted for ATs. Continued understanding of ATs' clinical practice in regard to AMI may help identify gaps in athletic training clinical education.

Disrupted somatosensory input alters postural control strategies during the Star Excursion Balance Test (SEBT) in healthy people

BACKGROUND

Chronic adaptations, including persistent sensorimotor deficits, remain in individuals with a history of ankle instability, resulting in altered postural control strategies during functional tasks such as gait, running, or landing. However, we do not know the contribution of the altered somatosensory input on postural control strategies during a dynamic balance task such as the Star Excursion Balance Test (SEBT).

RESEARCH QUESTION

The purpose of this study was to characterize postural control strategies with and without disrupted somatosensory input during a dynamic balance task in people without chronic ankle sprain.

METHODS

This study was a crossover study design. Twenty healthy young adults (10 men, 10 women; age = 23.9 ± 3.0 years, height = 174.2 ± 7.4 cm, mass = 71.2 ± 16.7 kg) performed the posteromedial reach test during the SEBT while standing on the ground and on foam. We measured the maximum reach distance (MRD); joint angles of the ankle, knee, hip, and trunk in the sagittal, frontal, and transverse planes; and position and displacement of the center of mass (COM) and center of pressure (COP) during the posteromedial reach task.

RESULTS

The MRD was shorter when standing on the foam than on the ground (p < 0.001). There was a condition by phase interaction for ankle dorsiflexion; tibia internal rotation; and trunk flexion (p < 0.001; p = 0.03; p = 0.01, respectively). The COM and COP were positioned more laterally on the foam (p < 0.001). The COM and COP anterior-posterior displacements were more anterior during the foam condition (p = 0.017).

SIGNIFICANCE

By using a foam pad to disrupt somatosensory information, participants demonstrated altered strategies to control the joint kinematics, COM, and COP, as a function of posteromedial distance. Ankle and trunk movement strategies may influence the posteromedial reach distance. This model may simulate changes that occur with chronic ankle instability.

Does Strength Training for Chronic Ankle Instability Improve Balance and Patient-Reported Outcomes and by Clinically Detectable Amounts? A Systematic Review and Meta-Analysis

OBJECTIVE

Strength training as a form of exercise therapy has long been used to maintain or promote strength, but its effectiveness as a treatment intervention in chronic ankle instability (CAI) is not fully understood. The purpose of this study was to evaluate the effects of strength training compared with no exercise and neuromuscular control training on balance and self-reported function in people with CAI.

METHODS

Eight databases (PubMed, Embase, Cochrane Library, Web of Science, EBSCO, PEDro, CNKI, and WanFang) were searched in June 2020. Randomized controlled trials (RCTs) involving strength training conducted on individuals with CAI were included. Data were extracted by 2 independent reviewers using a standardized form. Methodological quality and risk of bias were assessed by using the PEDro Scale. In addition, the GRADE evaluation system (Grading of Recommendations Assessment, Development and Evaluation) was used to determine the strength of evidence. A total of 554 studies were initially screened, resulting in a final selection of 11 RCTs involving 428 participants, and 8 RCTs were included in the final meta-analysis. Compared with no exercise, strength training demonstrated some benefits in the Star Excursion Balance Test (anterior: weighted mean difference [WMD] = 2.39, 95% CI = 0.60-4.18; posteromedial: WMD = 3.30, 95% CI = 0.24-6.35; posterolateral: WMD = 2.97, 95% CI = 0.37-5.57), but these intervention results did not reach the minimal detectable change values.

CONCLUSION

Available evidence showed that, compared with controls, strength training did not produce any minimal detectable changes on Star Excursion Balance Test or Foot and Ankle Ability Measure scores in individuals with CAI. Clinicians should use strength training cautiously for improving balance and symptoms in CAI.

IMPACT

The results of this study may have an impact on selecting effective physical therapy interventions for managing symptoms associated with CAI.

Current perception threshold testing in chronic ankle instability

BACKGROUND

Damage to sensory input is an underlying pathology of chronic ankle instability (CAI). Therefore, it is necessary to evaluate the sensory function of patients with CAI. The present study quantitatively evaluated sensory nerve function in patients with CAI and healthy controls using current perception threshold (CPT) measurements, as well as the influence of sex, age, and body mass index (BMI) on CPT values and the relations between CPT frequencies.

METHODS

Fifty-nine subjects with CAI and 30 healthy controls participated in this study. CPT values at the anterior talofibular ligament region were recorded on the injured and uninjured sides in CAI patients and on both sides in the healthy control group. Between group differences were compared. The influence of sex, age and BMI on CPT values was evaluated. Correlations between different frequencies were also studied.

RESULTS

There were no significant differences in age, sex, height, weight or BMI between the CAI and healthy control groups. The CPT values did not show a significant difference by sex. The CPT values did not significantly correlate with age or BMI. Compared to the control group, the CAI group had significantly higher CPT values on the injured and uninjured sides under 250-Hz and 5-Hz electrical stimuli; the difference between the groups was significant (p < 0.01), and the effect size were large. No significant difference was observed under 2000-Hz stimuli. There were correlations between CPT values at different frequencies (p < 0.01), especially 250 Hz and 5 Hz.

CONCLUSION

The present study revealed increased sensory thresholds in 250-Hz- and 5-Hz-related sensory nerve fibres in the injured and uninjured ankles of patients with CAI. This increase may indicate dysfunction of A-delta and C fibres. Sex, age and BMI did not significantly impact CPT values. There were correlations between CPT values at different frequencies, especially 250 Hz and 5 Hz.

LEVEL OF EVIDENCE

Level III, case-control study.

A comparison of mobilization and mobilization with movement on pain and range of motion in people with lateral ankle sprain: A randomized clinical trial

BACKGROUND

Maitland and Mulligan mobilization techniques are two manual therapy methods to increase the range of motion following immobility treatment. The present study was conducted to compare two therapeutic methods, namely mobilization and mobilization with movement (MWM), on the pain and range of motion in people with lateral ankle sprain.

METHODS

A total of 40 individuals with grade two lateral ankle sprain were randomly divided into two groups, including the Maitland's mobilization intervention group, and the Mulligan's mobilization intervention group. Both groups underwent treatment every other day for two consecutive weeks. The pain intensity was measured using the Visual Analogue Scale (VAS), and the ankle dorsiflexion movement range using the Weight Bearing Lunge Test (WBLT) before and one day after the intervention.

RESULTS

There were no significant differences between the two groups in terms of pain (P = 0.297) and range of motion (P = 0.294) before the intervention. Meanwhile, after the intervention, a significant change was observed in both groups in terms of these variables, which indicates the effectiveness of both interventions (P < 0.001) and the greater effect of the mobilization with movement in reducing pain (P = 0.037) and increasing the range of motion (P = 0.021).

CONCLUSIONS

Both techniques significantly improved the range of motion and reduced pain in people with lateral ankle sprain, but Mulligan's technique was significantly more effective among the two, perhaps due to joining active and passive mobilizing tensile forces as well as interaction of afferents and efferents in the reflex arc.

Alterated ligamento-muscular reflex pattern after stimulation of the anterior talofibular ligament in functional ankle instability

PURPOSE

Ligamento-muscular reflex pattern following stimulation of the anterior talofibular ligament (ATFL) was examined.

METHODS

The peroneus longus (PL), the tibialis anterior (TA), and tibialis posterior (TP) muscles were investigated in sixteen patients with functional ankle instability (FAI) and 16 age- and gender-matched controls. The ATFL was stimulated with a fine wire electrode while electromyographic (EMG) activities were recorded during isometric foot contraction of 20% maximal force in plantarflexion, dorsiflexion, supination and pronation. The complete measurement was repeated after a peroneal block anesthesia.

RESULTS

Statistically significant changes in post-stimulus EMG activity were observed in all three muscles and all four tested foot positions. In supination, the PL showed no reactions in both groups before and after anesthesia. The post-stimulus inhibition of the TA seen after 80 and 180 ms disappeared in controls after anesthesia. The TP had similar inhibitory responses in both groups.

CONCLUSION

Ligamento-muscular reflex pattern is alterated in FAI. While early reactions are essential in protecting the ankle joint in sudden movements, the later responses indicate a supraspinal control of neuromuscular stability of the ankle joint. Proprioceptive rehabilitation of the PL, TA, and TP is crucial in FAI to compensate for post-traumatic ligamentomuscular reflex deficiencies.

LEVEL OF EVIDENCE

II.

Exposure to impacts across a competitive rugby season impairs balance and neuromuscular function in female rugby athletes

Objectives

We used objective assessment tools to detect subtle neurological deficits that accompany repetitive and mild head impacts in contact sport across a season.

Methods

Female participants (n=13, 21±1.8 years old; 167.6±6.7 cm; 72.8±6.1 kg) completed assessments pre and post the varsity rugby season. A commercial balance board was used to assess static balance and response to dynamic postural challenge. Spinal cord excitability via the soleus H-reflex was assessed in both legs. Video analysis was used to identify head impact exposures.

Results

A total of 172 potential concussive events were verified across 11 athletes (15.6±11; 95% CI: 6.5 to 19.8). Balance performance was worse at post-season for total centre of pressure which increased by 26% in the double stance on a stable surface (t(12)=-2.33; p=0.03; d=0.6) and by 140% in the tandem stance on a foam surface (t(12)=-3.43; p<0.01; d=0.9). Despite that, dynamic postural performance was improved after the season (p<0.01). Spinal cord excitability in rugby athletes did not change across the season but deviated from normative values at baseline.

Conclusion

Quantitative measures revealed that exposure to impacts across a competitive rugby season impair balance in two specific stances in female rugby athletes. Tandem-leg stance on an unstable surface and double-leg stance on firm surface are useful assessment conditions when performed over a low-cost balance board, even without clinically diagnosed concussion.